This invention relates generally to textile fabrics having conductive polymer films thereon, and in particular to fabrics having a pattern formed by conductive and non-conductive areas.
Textiles, such as fibers, yarns and fabric, having a conductive polymer coating, are disclosed by Kuhn et al. in U.S. Pat. No. 4,803,096. These electrically conductive textiles have been suggested for use in the control of static electricity, attenuation of electromagnetic energy and resistance heating. For some applications, it has been found to be desirable to provide a textile fabric having anisotropic electrical conductivity. In Pittman et al, U.S. Pat. No. 5,102,727 and Gregory et al, U.S. Pat. No. 5,162,135, textiles having a conductivity gradient were prepared by blending conductive and non-conductive yarns, or by contacting the conductive textile with a chemical reducing agent, respectively. While satisfactory for some applications, the methods used to produce conductivity gradients do not readily lend themselves to the manufacture of more complex patterns.
Alternatively, patterned electrically conductive textiles, that is fabrics having a pattern of conductive and non-conductive areas, may be provided by selectively removing portions of the conductive polymer film with, for example, high velocity water jets, as in Adams, Jr. et al, U.S. Pat. No. 5,292,573 and U.S. Pat. No. 5,316,830. A characteristic of the water jet process is that some, but not all of the conductive polymer film is removed from the textile fiber. Accordingly, the difference in conductivity between treated and untreated areas of the fabric may not be as distinct as desired. Further, the process requires the use of relatively sophisticated equipment, which is not readily available.
A limitation on the application of conductive polymers in general has been their lack of stability to environmental conditions resulting in a decline in conductivity with age. The influence of temperature, humidity and oxidation level on the stability of conductive polymers was discussed in Munstedt, H., "Aging of Electrically Conducting Organic Materials", Polymer, Vol. 29, page 296-302 (February, 1988). It has been proposed to apply a protective film or laminate to the conductive polymer to exclude oxygen and otherwise limit environmental exposure. However, one of the advantages of conductive textile fabric is its flexibility, which may be diminished by the application of protective coatings to the fabric.